Electrical-heater resistance element



UNITED sTAT PATENT DFFICE.

WILLIAM E. GARDNER, or PITTSBURGH, PENNSYLVANIA, ASSIGNOR 0E ONE-THIRDTo .HENBY oLAY BLACK, or BEN AVON, PENNSYLVANIA, ANI) ONE-THIRD TOJULIUS JACOB, OF rrrrsnunen, PENNSYLVANIA.

' ELECTRICAL-HEATER RESISTANCE ELEMENT.

No Drawing.

long used, and which nevertheless is cheap' to produce and economicalto. use.

In general the invention consists in a re sistance unit composed ofnon-metallic, nonfusible and non-combustible substances under theheating current. More specifically, it comprises an electricalresistance element formed of a mixture of finely divided nonmetallicconducting and non-conducting substances, which will not fuse andtherefore remain. in their original condition no matter how long used.

Various substances can be used for the two elements of the compound. Asthe conducting element of the compound I prefer to use carbon, andpreferably that form of carbon found in substantially pure coke. For thenon-conducting element of the compound various substances can be used,preferably bone ash or bone earth, such as can be obtained on the marketin various grades,--that which is best for my purposes being the whitebone ash; or commercial carborundum may be used as the non-conductingelement. These ingredients will be mixed in a finely divided state,either granulated, but preferably in powdered form.

The finer the in redients the better, as it obviates any slig t arcswhich might form between the grains of granulated material. Satisfactoryresults are secured by reducing the ingredients to a size to passthrough a sixty-mesh sieve or finer.

These ingredients reduced to a fine state are then very thoroughlymixed, so that all.

the particles of the conducting material (carbon) are divided orseparated by particles of non-conducting material (bone ashSpecification of Letters Patent.

Applicationfiled July 7, 1919. Serial No. 309,133.

or carborundum, orboth). The more intimate the mixture the better theresult.

The proportions of the ingredients may be varied, depending upon theparticular use to which the heater is to be applied, and to the voltageand amperage of the current to which itis to be subjected. NVithhighvoltage currents obviously the proportion of the non-conductingorinsulating ingredient must be greater than for a low voltage current.Likewise the higher the resistance of the non-conducting ingredient theless the amount that need be used. In general I have found thatcarborundum must be used in a .slightly larger proportion than bone ash,as carborundumis not as good an insulator as bone ash. For ordinarypurposes .I have found that a mixture consisting of three parts ofcarbon to one part of bone ash (or a slightly greater amount ofcarborundum when the latter is used in place of bone ash) givessatisfactory results.

This composition can be used either in a loose dry form or can be formedinto a solid by the use of asuitable binder. It can be used in loose dryform by merely placing it in a tube composed. of electricallynonconducting but heat conducting material, or

in a metallic tube provided with a suitable electric insulating liningand having the two terminals ofthe electric circuit inserted into theends of the tube and into the powdered material; orsuch dry material maymerely be placed in an electric non-conducting pan or trough, such asone composed of porcelain or earthern ware, with the terminals of thecircuit inserted into the powdered material at opposite ends of said panor trough.

t can also be molded into solid form of any desired size or shape by theuse of a binder which is non-fusible under the heating cur rentand'which does not form too high a conductor of electric current. I havefound that if these dry ingredients are mixed with a very small quantityof molasses and then molded and carbonized at a high heat in a closedreceptacle a very solid and durable resistance element is formed.

These resistance elements can be connected in the circuit either inmultiple are or in series or in any other well known way of connectingelements in an electric circuit. They can be made of any desired sizeor? element between the electrical terminal) the larger should bethe'percentage of conducting material relative to the non-conductingmaterial.

A resistance element composed of the ingredients specified is cheap toproduce, is highly efficient in use, does not burn out as do metallicresistance elements, and furthermore is practically unaffected by theelectric current due to the fact that the elements do not fuse togetherunder a heating current but always remain in the condition of originalmixture.

l lhis resistanceelement can be used for any purpose or in any placeWhere an electrical resistance element for heating purposes can be used.

' Obviously various kinds of ingredients suitable for the purpose statedwill suggest themselves to those skilled in' the art. ikewise theproportions of these ingredients can be varied within quite wide-limits,depending upon the characteristics of the specific ingredients used, thevalue of. the current of the circuit in which 'the same is to beinserted, and the particular "use to which the heating element is to beput.

I claim: s

1. An electrical resistance element con sisting of an intimatemixture offinely divided dry carbon, and finely divided bone ash.

2. An electrical resistance element consisting of an intimate mixture offinely divided coke, and finely divided bone ash.

In testimony whereof I have hereunto set my hand.

WILLIAM GARDNER.

Witness v G. G. TRILL.

